Brake drum



Sept, 20, 1932. J, SNEED. 1,878,006

BRAKE DRUM Original Filed Aug-6, 1925 JOHN SNEED, or nn'rnor'r; MICHIGAN, ASSIGNOR "r II-IE MIDLAND STEEL r'nonuo'rs Patented Sept. 20, 1932 mooiv riinr, or CLEVELAND, OHIO, A CORPORATION or onto BRAKE nRuM 'briginal application filed. AugustG, 1925, Serial No.

1927. Serial prises to that extent a divisionof my copending application.

One of the apparent advantagesin the internal expanding type of brake is its freedom from grit or moisture. It has long been recognized that the presence of water between the friction surfaces may result in the loss of control of the car. The presence of grit between the braking surfaces causes a scoring and uneven wear which is .highly detrimental and greatly shortens the life of the brake.

'When a brake shoe is'urged into engages ment with a'flangecl' brake drum, there is a tendency todistor-t the drum. If the drum be permanently distorted theefiect will be to vary the clearance between the shoe-and the drum so that an uneven engagement may result; The .clearance'ma'y be reduced to so little that a" continuous drag results, with consequent danger of heating and freezing of the brake. It is therefore among the objects of my invention to form abralre drum of great strength consistent with' minimum weight which will eflecti-vely resist distortion and permit high braking pressures which might be non-uniformly exerted on the drum flange.

Another object is to position the reinforcing or strengthening means for the drum with relation to the backing'plate to exclude foreign matter from the 'inside of the drum. Another objectis to form the backing plate with regard to both the brake drum and the brakeshoe' to cooperatein carrying out the above object. v

Other objects will appear from the following more detailed description of my invention. The essential characteristics are summarized in the claims. 7

In; the drawing Fig. 1 is a partly broken elevation taken from the inner side i..e. facing thebacking plate; Fig/Qjis a section taken along the line 2-2 of Fig.1; Fig. 3 includes 48,470. Divided aid this application filed. June 8, No. 197,329.

three diagrammatic illustrations of drum dis.- tortion..

In the drawing I designate the drum having an outward face A and having'the primary flange F. Concentric with the flange I show the shoeS which may be of any illustrative type. For convenience of designation I consider the face A of the drum as being on the outer side of the drum so that the flange F extends inwardly, that is, toward the center of the vehicle. The drum is flanged radially to provide an annular web W which serves as a radial reinforcement for .the inner portion Such a radial flange is common and has been thought heretofore to be adequate to support the flange. It has been my experience however, that when the shoe'F is forcibly expanded that the'web W tends to ripple or wave in a circumferential direction with the result that the inner portion of the flange F may be forced to describe an el1ipse,-while the outer portion of the flange F adjacent the face A is held to a circle. My experience has taught me that the web W or its equiv alent alone is inadequate and that a harmful distortion of the drum is not prevented by itsuse alone.

In Fig. 3, I have shown diagrammatically the rippling or waving of a radial web at the brim of a distorted-drum. Theviews a and b are'taken at right anglesto each other along the minor and major axes of the ellipse formed by thebrim of the drum when it is distorted. Diagram 0 represents the normally formed drum. 7

a To gain the desired stability and to stay within the limits of economy both of material and of manufacture, I have found it advantageous to form a second cylindrical flange FF which extends inwardly of the drum and lies coaxially of the flange F. The flange FF is integral with the web W and is adapted by reason of its position or rather by reason of its cylindrical shape, to withstand axial strains or forces" delivered to it which are parallel to the axis of the drum. The tendency of the web W to ripple or wave delivers such strains to the flange FF in the form of unbalanced couples lying in the cylinder described by theperiphery of the web. I

may conceive that these couples are measured between the nodes and troughs of the waves or ripples set up or tended to be set up in the web. The componentsof these couples,

' as mentioned above, lie in a cylinder of the periphery of the weband are taken up in the directionof axial dimension of the flange FF. The flange FF prevents-rippling of the ing plate P is made of material of sufficient weight to take the reactive torque from the brake shoe and deliver it to the axle of the 7 vehicle. In such a backing plate the middle portion is formed to be secured to the axle or steering knuckle as the case may be. For

the purpose of my present invention, I am concerned with that annular portion of the backing plate which lies near the surface of the shoe S and extendsradially and inwardly (relative to the vehicle) toward the brim of the drum. The backing plate may lie close to the shoe and serve to guide it as at 1. The peripheral portion of the backing plate comprises an annular ofl'set portion 2, which includes a circumferential flange 3 and a radial flange'l. The inwardly facing surface of the radial flangel may lie in substantially the plane of the brim of the drum. The radial dimension of the flange 4 may conform to the depth of the web W so that a clearance is provided between the backing plate and theflange FF of the drum as at 5.

The radial dimension of the "web W and consequently the flange 4 determine the dis tance between the opening 5 and the surface of the shoe S. Inasmuch asthe'flange FF lends strength to the web W, the web may be given a greater dimension than has heretofore been found practical. The result of this is that a comparatively long and tortuous path must be traversed by moisture or grit which is thrown into the opening 5. Opposed tothe ingress of such moisture or grit, is the centrifugal force caused by rotation of the drum. It has been my experience that the combination of a drum so formed with a backing plate as shown comprises a highly effective protection against extraneous matter.

From the foregoing description of my invention. it appears that I have provided a drum of great strength for a minimum gauge of material and one that is susceptible of cheap and eflicient manufacture. The rigid c ity of the drum permits a smaller clearance between the brim of the drum and the back- 111 pl dtely excluded. I have shown herewith a preferred form of my invention, but I do not care to be limited other than by the claims appended hereto. I

I claim: 1

1. The combination of a brake drum for a vehicle brake having a main cylindrical flange and an L shaped flange formed on-the open inner edge thereof and facing inwardly with respect to the vehicle, and a relatively fixed member having an annular part proximate the said L shaped flange for excluding, foreign matter from the drum said relatively flxed member lying at least radially within the said L-s'ha ed'flange.

2. The com ination of a brake drum having an L shaped flange extending beyond the open inner edge of the said drum and a backing plate having its periphery disposedin close proximity to and within the centrally facing portion of the L shaped reinforcing flange.

3. The combination of a brake drum having an L shaped flange extending beyond the body of the drum and forming the brim thereof, and a backing plate having its periphery disposed in close proximity to. the V centrally facing portion of the L shaped reinforcing flange, said backing platelying substantially within the plane of the brimof the drum.

4. The combination of a brake drum having a main cylindrical flanged portion and a cylindrical reinforcing flange of greater diameterthan the main'flange and lying concentric therewith, and a backing plate the periphery of which extends beyond the diameter of the main cylindrical flanged portion and lies in close proximity with and within the said auxiliary reinforcing flange.

5. The combination of a brake drum having a main cylindrical flanged portion and an L shaped reinforcing flange formed on the plate so that foreign matter is more com- I inner edge thereof, and a backing plate having an annular peripheral off-set portion disposed in close proximity to and radially within the centrally facing portion of said L shaped reinforcing flange. v V r 6. The combination of a pressed metal brake drum having a main cylindrical flange providing a cylindrical braking surface, a brake shoe disposed in operative'relation to said braking surface of the drum, a backing plate disposed adjacent the said brake shoe 1 and engageable therewith adjacent the periphery thereof and adapted to limit the lateral movement thereof, said brake drum having an L shaped reinforcing flanged portion formed on the inner open edge thereof, the backing plate having an annular inwardly off-set portion extending beyond the cylinder described by the braking surface of the drum and into close proximity with the centrally facing portion of the said L shaped reinforcing flange.

7 A brake drum formed of relatively light sheet stock and pressed to shape having a main flange providing a braking surface and a cylindrical reinforcing flange lying concentric with said main flange and being of greater diameter than said main flange and extending beyond said main flange, and being joined integrally with said main flange whereby the full strength of the stock is developed and the drum is held against distortion, in combination with a back plate the periphery of which is proximate to and radially and axially within the said cylindrical reinforcing flange.

8. A pressed metal brake drum formed of light sheet stock comprising a main cylindrical portion providing a braking surface, a radial web formed at the edge of said main cylindrical portion, a reinforcing cylindrical ring for said web of substantially the same size of said web and formed integral with said web and lying concentric with said main cylindrical portion and extending inwardly of said drum, whereby the ring reinforces the 7 web and develops the full strength of the stock while holding the drum against distortion.

9. A pressed metal brake drum formed of relatively light sheet stock having two integrally formed auxiliary reinforcing flanges after flanges of substantially the same size, one of which is formed on the brim thereof, said auxiliary flanges being disposed at right angles to each other and mutually supporting each other, one holding the other from rippling and the latter holding the former from radial distortion.

In testimony whereof, I hereunto afl'ix my signature.

JOHN SNEED. 

